Cellular structures

ABSTRACT

A cellular structure includes a plurality of interconnected cells of fabric material. The cells are at least partially filled with a composite fill material that includes a particulate material and a bonding agent. A cellular unit made up of a plurality of the interconnected cells may have an associated load-bearing frame to enable lifting and/or transportation of the structure. The fill material is preferably resilient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims benefit under 35 USC120, to international application PCT/GB2009/000673, filed Mar. 11,2009, which claims the benefit of Great Britain application no.080448.7, filed on Mar. 11, 2008. International applicationPCT/GB2009/000673 is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to cellular structures, in particular tocellular structures including a composite fill material.

BACKGROUND

Cellular confinement systems are commonly used in civil engineeringapplications for land reinforcement, erosion control, embankmentstabilisation, retaining structures and channel protection. Cellularsystems such as those available from the UK company Terram Limited aremade from various grades of thermally bonded nonwoven geotextilematerial. Such geotextile materials have the flexibility of a fabriccombined with a high tensile strength and relatively high stiffness.They are water permeable so soils are prevented from intermixing whilestill permitting water to flow freely through the system.

Geotextile cellular systems can be used to confine all kinds ofaggregates, soils, sand, etc. of any particle size. They are commonlyused in a single layer to help prevent erosion by confining soil onslopes. For example, the ‘Erocell’ system from Terram Limited can beused in the prevention of topsoil erosion on slopes. Cellular systemsprevent horizontal movement of the confined material, substantiallyimproving the material shear strength and bearing capacity. They can beused to form access roads, hard standings, embankment slopes,containment dykes and levees, landfill lining and covers, dam faces andspillways, noise abatement walls and parking areas. Alternatively, suchcellular structures can be stacked in order to support slopes, constructwalls, or form other defensive and protective structures.

Such geotextile cellular systems are typically collapsible, which allowsthem to be transported flat, deployed on-site and filled on demand.However, the time and energy (manpower, machinery, etc.) required tofill the cellular structure is desirably offset against the convenienceof flat-pack delivery. Such systems may not always be suited tosituations where it is desired to form a solid structure such as a wallor barrier relatively quickly.

Furthermore, the structural properties of a structure resulting from thefilling of a cellular system will depend on the fill materials used,which are usually limited to locally available fill materials, and onthe filling method. Whereas larger aggregate materials may allow forfaster filling, such fill materials may not always be suitable where thecellular structure is required to act as a more robust impact barrier orin some ballistics defence applications, for example. A problem withfiner particulate fill materials such as soil or sand is that they havefree-flowing or liquid characteristics, making them potentially moredifficult to handle and constrain in some situations.

SUMMARY

From a first aspect the present invention provides a cellular structureincluding a plurality of interconnected cells of fabric material, thecells being at least partially filled with a composite fill materialincluding a particulate material and a bonding agent.

Thus the invention can provide a pre-filled, three-dimensional structurewhich combines the support and reinforcement of a cellular fabricstructure with the desirable physical properties of a composite fillmaterial.

The cells are preferably directly interconnected to one another by thefabric material. Preferably the cells each have fabric walls in commonwith adjacent cells. The structure is preferably in the form of acellular unit having at least three and preferably at least four rows ofcells, each row including at least three and preferably at least fourcells. Preferably the cellular unit includes a single layer of suchcells.

Preferably the composite material provides a solid, rather than fluid,fill. However this does not mean that the fill material is desirablyrigid or inelastic, as will be explained below. The bonding agentpreferably bonds together the particulate material, which is distributedthroughout the fill, and also preferably bonds the composite fillmaterial to the fabric material of the cells. The composite fillmaterial can have the relatively high density and uniformity of aparticulate material but with structural integrity and stabilityprovided by the bonding agent. The particulate material is bound in thecomposite and cannot escape, allowing it to be exposed in open cellswithout the need for sealing or covering means, if desired. The presentinvention thus allows a particulate material, such as sand, to becontained within an open cellular structure and for the structureso-filled to be transported and deployed immediately on site without theneed for erection, filling and compaction. The pre-filled cellularstructure can be rapidly deployed and instantly used as a wall, barrieror other defense structure, for example. One or more of the cellularstructures or units may be stacked side by side and/or on top of oneanother. Applications may include civil defense e.g. vehicle barriers orflood protection and military defence e.g. ballistics protection.

The structure is advantageously formed of a plurality of interconnected,high mass units which result in strength and resilience to impact, shearforces and rupture. The overall structural properties can advantageouslybe adjusted by the choice of composite fill material. Moreover the cellsare filled during the manufacturing process, enabling the structures tohave uniform and reproducible characteristics. The variability ofon-site fill materials and methods is eliminated.

The bonded composite fill material may not completely fill the cells ofa structure. The composite fill material including a particulatematerial and a bonding agent preferably forms a base and/or upper filllayer for the cells. This aids containment of the fill, especiallywhere, as is preferred, the cells are open at the top and/or bottom. Insome embodiments at least, the rest of the cells may be filled with adifferent material. The other fill material preferably does not includea bonding agent. The unbonded fill material may be loose or fluid. Aparticulate fill material is still preferred to enable filling andachieve a high density. However, such an unbonded fill material maycontain a binding agent such as fibres to increase cohesion. The cellsmay therefore include a mixture of bonded and bound fill materials. Thebenefits of fibre binding and/or reinforcement are discussed in moredetail below.

It will be appreciated that the fabric material of the cells ispreferably flexible and thus the structure may not be entirely rigid. Ageotextile nonwoven material is preferred. It is preferable in manyapplications that the composite fill material is also resilient,providing a cellular structure which has a degree of flexibilityoverall. Preferably the bonding agent resiliently binds the particulatematerial so as to retain a desired degree of flexibility. The bondingagent is therefore preferably elastomeric when set. Thus according to apreferred embodiment the entire structure can react resiliently tolateral and longitudinal displacements and shear forces resulting fromimpact. In other words, the structure is shock absorbing and impactresistant. This can make the structure particularly effective againstvehicular penetration, e.g. for use in crash barriers. The structure mayalso be able to withstand an explosive blast and find use e.g. in bombshelters and bunkers.

A preferred resilient structure includes a compliant, undulating outersurface. This surface may be provided by partly cylindrical cells on itsouter sides. The interior of such a structure may be divided intomultiple interior cells by intersecting internal fabric walls, e.g.formed from strips. Such a structure can provide a cushioned outersurface particularly suitable for use as a crash barrier, bunker, or thelike. The undulating outer surface can advantageously enhance theresilient response of the structure and could even result in deflectionof an impacting body.

The preferably resilient structure may also be used in ballisticsprotection. In particular, it has been found that small-arms fire suchas bullets will be slowed as they pass through the resiliently flexible,energy-absorbing structure and even stopped. The bullets areadvantageously absorbed and become embedded in the structure withouttearing it apart, whereas e.g. concrete blocks would crack and shatterunder fire. The composite fill material has been found to providesuperior ballistics performance and better stability when compared to aloose sand fill. Even if the fabric material is ruptured under fire, thebonded composite will not leak out.

The preferably resilient structure may advantageously absorb or containa blast without shattering or breaking upon impact. This represents animprovement e.g. over concrete.

The cellular fabric matrix helps to maintain structural integritydespite multiple impacts and bullet penetrations, for example.Furthermore it is apparent that even if one of the cells in thestructure should be damaged or ruptured in some way, the effect on theoverall strength of the structure can be minimal as the other cellsremain intact. Blast resistance can be high. Where ballistics andexplosions are involved, there is the advantage that the fabric andcomposite fill materials will not create metal shrapnel if hit.

A further advantage of the structure's resilient flexibility is that itis able to conform at least partly to the shape of a surface on oragainst which it is placed. As a consequence the surface contact areaand hence the surface friction resisting movement of the structure underimpact is maximised. This represents a significant advantage over othersolid and inelastic units used to build walls, barrier, defenses, etc.such as concrete breeze blocks. Resiliently flexible structures inaccordance with the preferred embodiment may be considered to providethe conformability of traditional sand bags but with additionalelasticity and the extra strength of an interconnected cellularstructure.

The high coefficient of friction that the flexible cellular structuregenerates when contacting another surface can also aid vertical stackingof the structures to form sheer walls and upright barriers of anydesired height. Whereas cellular structures filled with fine particulatematerial such as soil or sand typically have to be stacked withsubsequent layers stepped back from one another, in order to stabilisethe stack, resiliently flexible cellular structures in accordance withthe preferred embodiment can be stacked directly on top of one anotherto form vertical walls. Furthermore particulate material cannot leak outbetween the layers where it is retained by the bonding agent in thecomposite fill material. A seal is advantageously not required betweenadjacent layers of stacked cellular units, as the fill material ispreferably solid, at least at the exposed surfaces of the fill. However,in a set of less preferred embodiments, an overlapping strip or ‘skirt’may be provided between the cells e.g. to help with alignment and/or tostrengthen the stacked structure. In preferred embodiments, on the otherhand, there is no sealing means arranged between vertically juxtaposedcellular structures.

When several cellular structures or units are stacked side-by-side andvertically to form larger barriers and walls, the preferably resilientlyflexible units will conform and provide many points of contact betweentheir adjacent surfaces. Such a stacked structure is therefore lesslikely to break apart under impact, for example as compared to a barrierbuilt from rigid concrete blocks.

The bonding agent is preferably an elastomeric material, such as arubber-based adhesive. The rubber material may be a synthetic rubber butpreferably it is a natural rubber, for example a latex rubber. Bothnatural rubbers and synthetic rubbers are readily and cheaply availableand therefore production costs are minimised. Alternatively, the bondingagent may be a non-flexible resin including flexible particles, theparticles being formed from rubber for example, so that the materialoverall is elastomeric. In another alternative the bonding agent may notitself be initially elastomeric but it may form an elastomericcross-linked network upon curing.

The bonding agent may include a curable material. In the case of awater-based adhesive, such as latex adhesive, curing is achieved bydrying. Heat sensitive catalysts may be added that enable the bondingagent to cure and the composite material to set at relatively lowtemperatures e.g. 45° C., and not necessarily by removing all of themoisture from the material. However it has been found that therelatively large volume and mass of the filled cells do not make iteconomically feasible to dry the composite material using heat to curethe bonding agent. It is therefore preferred that a catalyst is used toinitiate chemical cross-linking of the bonding agent, preferably withoutheating. Any appropriate catalyst can be used; one suitable catalyst forcuring natural latex rubber is calcium chloride granules.

Preferably the composite fill material is permeable to gas and liquid.The particulate material and bonding agent may be mixed and formulatedsuch that individual particles are lightly coated with the bonding agentensuring that the spaces between adjacent particles remain open to thepassage of fluids. Additionally or alternatively the bonding agent mayshrink during curing, causing it to recede from significant portions ofthe surface area of the particulate material. Thus the natural porosityof the original loose particulate material may be preserved or evenincreased relative to a compacted fill of unbonded particles.

It is preferred that the fabric material of the cells is also gas andliquid permeable, for example a geotextile material is preferably used.In preferred embodiments the structure is therefore resistant towater-logging and will not become significantly heavier when wet. Byallowing the movement of water and nutrients vegetation may also beencouraged to grow, depending on the composite fill material. Suchvegetated structures can provide increased strength through the rootstructure and result in a more natural finished appearance, compatiblewith the local environment and ecology.

A permeable cellular structure in accordance with preferred embodimentscan advantageously be used to form flood protection barriers. Afterstopping the initial flood impact, water can drain through thepreferably permeable material of the cells and filler, leaving behind asolid protective barrier.

The particulate material may be any suitable natural or syntheticparticulate material. The composite fill material is versatile in termsof the materials from which it may be manufactured, e.g. depending onits end use. The particulate material is preferably sand, although othermaterials such as zeolite, recycled glass, carbon or the like may beused instead or in addition. More than one type and/or size ofparticulate material may of course be used e.g. a combination of sandand zeolite.

Additional reinforcing material such as fibres may be included in thecomposite. A fibrous material may act as a binding agent for thecomposite. The fibres may be formed of any suitable material, such as amaterial that is relatively inert and impervious to water. For example,chopped synthetic fibres such as polypropylene fibres or similar may beadded to the composite fill material. Such fibre reinforcement has beenused in concrete for many years and is also known to provide soilstabilization. Additionally or alternatively, natural fibres, steelfibres and/or glass fibres may possibly be used. Such fibrous materialmay increase the structural integrity of the composite fill and improveits load bearing and shearing strength, while also helping it to beelastic and flexible. Cells filled with the composite may therefore havegreater impact, abrasion and shatter resistance, and improved shockabsorbing and cushioning characteristics.

The fibres may be uniformly distributed and/or randomly oriented. Thereinforcing and/or binding character will depend on various factors suchas the fibre material, geometry, distribution, orientation and density.The fibres may be in the form of monofilaments or a fibrillated tape.Relatively short length fibres may be preferred, for example fibresbetween 0.5 and 10 cm in length, preferably between 0.5 to 1.5 cm inlength. The fibres may contain filaments which range in size from about8 dtex up to a few hundred dtex, where the unit decitex (dtex) is themass in grams per 10,000 meters of a single filament. Up to 5% by weightof fibre may be included in the composite. The amount of fibre is chosento provide a desired reinforcing and/or binding effect. The addition offibres to the composite may also improve its water distributionproperties. Such fibre material may also be used in other fill materialswhich do not contain a bonding agent, for example in a cellularstructure provided with a mixed fill, as is described above. The fibrespreferably act as a binding agent in a non-bonded fill material.

The particulate material may be formed from substantially sphericalparticles or other particle shapes. For example, a spherical particulatematerial may be preferred due to its ability to provide a uniformdistribution of particles in a lattice-like configuration.Alternatively, non-spherical particles may be preferred due to theirirregular shape which may provide a non-complimentary stackingconfiguration thereby enhancing the natural porosity of the particulatematerial.

The particulate material may be uniformly distributed throughout thecomposite. A uniform distribution may provide a consistent performance.

The appropriate bonding agent to particulate material mixing proportionsmay depend on a number of application-specific factors which mayinclude: the particle shape, size and type of particles; the bondingagent type; the desired degree of porosity; and the desired degree offlexibility for the end use of the structure. The ratio of the bondingagent to the particulate material may range from 1:7 to 1:15 by weight.Preferably, the mixing ratio is such that sufficient bonding agent isapplied to coat at least some part of the surface of each particleduring a mixing process but insufficient to fill the voids between theparticles, thereby retaining as many as possible of the natural physicalproperties e.g. porosity of the loose particulate material. In apreferred example the composite fill material includes a mixture of sandand approximately 8% by weight of adhesive such as natural latex.

The mean mass aerodynamic diameter of the particulate material may rangefrom 0.075 mm to 2.6 mm. The particulate material may include coarsesand (particles having a size of about 0.5 to 2 mm) and/or fine sand(particles having a size of about 0.05 to 0.5 mm). The size of theparticulate material may be dependent upon the intended application ofthe structure.

Turning to the overall structure, the cells can be open, meaning thatthey have no top or base wall of fabric material, i.e. the compositefiller material is only constrained in two dimensions and is exposed atthe top and bottom surfaces of the structure. However, the top and/orbottom surface of the structure may be provided with cover means toprotect the fill material from the external environment and/or to assistin handling.

In one embodiment the cellular structure may include a base formed of apreferably flexible material which can assist with the filling andmanufacturing process. For example, the cellular structure may be formedon a piece of flexible material which forms the base of the structurebefore the fill material is introduced. A base layer could instead beinserted inside the cells before filling. The presence of such a baselayer of material may improve the stability of the exposed composite. Itis preferable that such a base layer will not interfere with theflexibility of the composite and thus the surface friction. Alightweight and flexible mesh material may be used, e.g. a PVC-coatedpolyester mesh.

It will be appreciated that a pre-filled cellular structure inaccordance with the present invention may have a significant mass,particularly when the fill material includes a fine particulate materialand thus has a relatively high density. This is advantageous for formingsolid, immovable and indestructible barriers etc. However it can bedifficult to lift and transport such high mass cellular units. It may bepossible to use a fork lift truck, grabber, bale spike or other loadlifting apparatus to bear the load of the cellular unit and enabletransportation. However such machinery could damage the cellular unite.g. by piercing or tearing. Where the cellular structure is flexible,as if preferred, this can make it more difficult to grip and handle. TheApplicants have therefore devised a system which enables the load of acellular unit to be supported for lifting and transportation. Accordingto preferred embodiments the cellular structure, or each cellular unitof a cellular structure, has an associated frame for bearing the load ofthe unit.

It will be appreciated that such a load-bearing i.e. weight-supportingframe can be useful for any filled cellular unit, regardless of the fillmaterial, e.g. as long as the unit is sealed to prevent the fillmaterial from escaping when the unit is lifted. Advantageously theload-bearing frame may itself form a sealing base on which an opencellular unit can rest. For example, a frame could be used to form abase before the cellular unit is filled. This feature is thereforeconsidered novel and inventive in its own right and thus from a secondaspect the present invention provides a cellular structure including oneor more cellular units, each unit made up of a plurality ofinterconnected cells of fabric material and the cells being at leastpartially filled with a fill material, wherein each cellular unit isassociated with a frame for bearing the load of the unit. From a furtheraspect the present invention provides a method of forming atransportable cellular structure including: providing a frame; providingan open cellular unit including a plurality of interconnected cells offabric material on or in the frame; at least partially filling thecellular unit with a fill material; and using the frame to support theweight of the filled unit to enable lifting and/or transportation of thestructure.

It will be understood that the load-bearing/weight-supporting frame cantake many different forms as long as it is able to support and transmitthe load of its associated cellular unit, e.g. enabling the unit to belifted and carried via the frame. Such a load-bearing frame is distinctfrom a framework which may be used to merely peg out or expand thecellular unit for filling, or a surrounding framework which merelyhouses the cellular unit.

Often the filled cells will be at least partially deformable rather thanrigid, due to the fabric material preferably being flexible and thenature of the fill material. A particulate fill material e.g. sand maybe typical in some applications. In other applications the fill materialmay be a resilient material. The cellular unit may therefore bedifficult to grip and handle. The load-bearing frame can assist withsupporting the cells and enable easier transportation.

Where the fill material is loose or fluid rather than solid, it ispreferred that the frame provides a base for the open cellular unit,acting to seal it closed and prevent the escape of the fill material.The frame could provide a support plate on which the cellular unitrests, the plate forming a base for the cells. Alternatively a piece ofmaterial may be inserted inside the frame prior to placing the opencellular unit on or in the frame so as to form a base to the cells. Thebase may optionally be sealed before, during or after filling. This canallow the frame to have a more open structure. Even where the fillmaterial is solid it may be desired that the base of the cells is closedby the frame or a sheet provided within the frame, e.g. in order toprotect the exposed fill rather to prevent it from escaping.

In preferred embodiments the fill material provides a resilient fillincluding a composite material, as described hereinabove. Preferably thefilled cell are open at the top and bottom of the cellular unit. In itssimplest form the frame could include a single cross-piece passingunderneath the unit. However it is preferred that the frame includes atleast two cross-pieces, preferably at 90° to one another, so as toprovide torsional stability. Such cross-pieces could be arranged to passfrom side-to-side or corner-to-corner. Additionally or alternatively theframe may provide support around the base perimeter of the unit.Preferably the frame is arranged such that the surface contact betweenthe preferably resilient cellular unit and the ground is notcompromised.

The frame could provide a flat support e.g. bed frame or plate on whichthe cellular unit rests. Suitable load bearing ropes, chains etc. couldbe attached to the flat frame member for lifting. A surrounding framewith a lip underneath the base of the cellular unit could be sufficient.However it is preferred that the load-bearing frame includes one or moreupstanding members e.g. extending generally vertically against thecellular unit and/or one or more side members extending generallyhorizontally across the perimeter of the cellular unit. Such members canallow for easier attachment to load bearing means and can spread theload. Furthermore such upstanding and/or side members can be used toconnect an upper load-bearing frame over the top of the cellular unit,for example to facilitate lifting by a fork lift truck, crane orHIAB-equipped lorry.

It has been appreciated that a load-bearing frame including upstandingmembers and/or side members can provide the further advantage ofenabling cellular units to be coupled via the frames side-by-side and invertically stacked arrangements, to build up cellular structures made ofseveral units. Any suitable coupling means can be provided, e.g., clips,form-locking, nuts and bolts, etc. In one example, each frame includesan integral system of sockets and holes that can allow adjacent units tobe coupled to one another, e.g., by means of flat or shaped metal linksand bolts. Flexible connectors such as wire or rope can also be used,especially when the units are arranged on uneven ground. Integrallinking or connection members may also be provided.

The load-bearing/weight-supporting frame can be relatively rigid and insome applications this may advantageously stiffen the cellularstructure, especially when the fill material is flexible and/orresilient. However it is preferred for many applications that theload-bearing frame is flexible. While the individual frame members mayeach be rigid, e.g. metal bars or cross-pieces, the overall frame ispreferably arranged so as to be able to flex/twist and move in anoverall flexible and compliant fashion with the cellular units, e.g.upon impact. This can minimise the stresses on the individual structuralmembers and connecting components, and help to transmit forcesthroughout the structure. In the case of a crash barrier or blastprotection unit this can ensure that the presence of the frame(s) doesnot detract from the shock absorbing ability of the structure. Where aresilient e.g. composite fill material is used, as is preferred, theframe is preferably designed not to restrict the inherent flexibilityand resilience of its associated cellular unit. Shock absorbing andblast resistance properties are preferably not compromised.

The flexibility of the frames can also help the structure to adapt toirregularities in the surface on which it is deployed. As noted above,maximising the surface area in contact with the ground increases thesurface friction and helps the structure to resist movement underimpact.

The load-bearing frame can also aid the manufacturing process, assistingwith alignment and deployment of the cellular unit prior to filling. Itis also envisaged that any gaps or spaces between the cellular unit andits frame may be filled with the same or a complementary fill material.This can enable the cellular unit and frame to be manufactured as anintegral unit. It also advantageously increases the mass of each unitand can help to ensure even transmission of forces throughout thestructure. Where, as is preferred, both the cellular unit and frame areflexible, using a resilient fill material to couple the cellular unit tothe frame adds to the elastic shock absorbing response of the overallstructure. Encapsulating the cellular unit in flexible e.g. compositefill material within its associated frame can also increase the surfacearea with the ground or other contacting surface. Filling the spacesbetween the cellular unit and the frame can be assisted by inserting abase layer into or beneath the frame, underneath the cellular unit,before filling, e.g. a base layer as described hereinabove.

All of the features and advantages described hereinabove with respect tothe first aspect of the invention can be applied equally to a cellularstructure including one or more cellular units having load-bearingframes. However, it will be appreciated that a structure in accordancewith the second aspect of the invention is not limited to the use of acomposite fill material, nor to the use of a particulate fill material.For example a suitable elastomeric resin or foam might be used.

Some general features will now be described in accordance with bothaspects of the invention. The cells may be formed of any suitable fabricmaterial exhibiting strength and flexibility, including woven, knittedand nonwoven fibrous webs. The fabric preferably includes a nonwovenmaterial, further preferably a flexible nonwoven material. Suchmaterials are often chosen for their durability. The basis weight may bein the range of 200 gsm to 1000 gsm and is preferably 320-350 gsm. It isfurther preferred that the nonwoven is polypropylene-based. Aparticularly preferred material is a non-woven fabric formed frombi-component fibres, e.g. polypropylene and polyethylene fibres,geotextile materials manufactured by Terram Limited. One such suitablematerial includes 70% polypropylene and 30% polyethylene. Thesematerials have very good tensile strength, stiffness, punctureresistance and tear resistance, combined with flexibility. They may alsobe permeable to liquid.

Suitable fabric materials include spunbonded polypropylene nonwovens andother nonwoven and woven materials. Another example of a preferredmaterial is a thermally bonded polypropylene nonwoven material such asis available from the US company Fiberweb™.

In a preferred embodiment the interconnected cells are formed from oneor more interconnected continuous strips of fabric material. Thestrip(s) are folded back and forth, or layered against one another,adjacent parts of the strip(s) being bonded to each other at spacedapart locations such that the material defines an interconnectedcellular unit. The cells so-formed are preferably tubular with thebonding points defining the corners of a generally square cross-section.The external cells in a unit may be bonded at fewer locations and arepreferably partly cylindrical, e.g. defining a curved outer surface,especially when filled.

Preferably the cells are formed by applying an adhesive between thestrip layers. Joints formed in this way have been found to be as strongas a nonwoven material itself. A special adhesive is preferred which canretain its bonding strength across a wide temperature range includingextreme cold and extreme heat as found in some countries of the world.

Where cellular units are formed from a single strip, folded back andforth on itself and bonded, the ends of the strip is desirably removedor glued down. In other embodiments the cells (which are preferablytubular) may be manufactured individually and then interconnected attheir corners and/or along their edges by any suitable means to give acellular unit, e.g. containing 21 interconnected cells. The individualcells may be sewn together to form a unit of interconnected cells.

The fabric material may be treated either during or post manufacture toimprove certain properties and/or appearance. For example, where thesystem may undergo prolonged exposure to sunlight the UV resistance ofthe fabric may be enhanced by adding appropriate stabilisers.

The cellular units or structures can be made on any macroscopic scale,although the invention has been found to apply in particular tostructures having cell dimensions of the order 100-700 mm in diameterand 500-3000 mm deep. As the structures are pre-filled duringmanufacture rather than being filled on site, the cell dimensions can bereduced relative to known cellular structures, providing a comparableperformance in a more compact structure. The interconnected cells may bemanufactured so as to have any suitable shape such as triangular,rectangular, etc. However the cells are preferably circular or polygonalin cross-section. In preferred embodiments the cells are about 250 mm indiameter and 750 mm deep.

A yet further aspect of the invention provides a cellular unit for usein constructing a shock absorbing barrier or other resilient structureincluding at least three adjacent rows of interconnected tubular cells,each row including at least three interconnected adjacent cells, thecells being formed by a flexible nonwoven fabric and containing aresilient fill material. The resilient fill material preferably includesparticles bonded within a resilient matrix formed by a bonding agent.The particles and/or the bonding agent may be elastomeric.

It is preferred that at least the external cells of the unit are partlygenerally cylindrical, so the external walls of the unit are undulating.Such an undulating outer surface can advantageously provide a cushioningeffect and possibly act to deflect an impacting body. This aspect of theinvention can additionally include any of the preferred featuresdiscussed above in relation to the first and second aspects thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Some preferred embodiments of the present invention will now bedescribed, by way of example only, and with reference to theaccompanying drawings, in which:

FIG. 1 shows a schematic perspective view of a prior art cellularconfinement system;

FIG. 2 shows a schematic perspective view of a cellular structureincluding a fill material in accordance with an embodiment of theinvention;

FIG. 3a shows a schematic plan view of a cellular unit;

FIG. 3b is a perspective view of the cellular unit of FIG. 3 a;

FIG. 4 shows a schematic exploded view of two stacked cellularstructures in accordance with an embodiment of the invention;

FIG. 5 shows a schematic perspective view of a filled cellular unit andassociated frame in accordance with a preferred embodiment of theinvention;

FIG. 6 is an exploded view of the cellular structure of FIG. 5;

FIG. 7 shows the cellular structure of FIG. 5 with the addition of alifting frame; and

FIG. 8 shows a barrier or wall formed from the cellular structures ofFIG. 5.

DETAILED DESCRIPTION

There is shown in FIG. 1 a prior art cellular confinement system 1including a number of interconnected cells 2 formed from a fabricmaterial such as a nonwoven geotextile available from Terram Limited.For civil engineering applications such as erosion protection the celldiameter is typically 25-45 cm and the cell depth is typically 10-15 cm.For example, the ‘Erocell 25’ product manufactured by Terram Ltd. isavailable in a panel measuring 10 m×7 m and containing around 1900 cellssized 25×25×10 cm. The flexible panel is collapsed into a flat state androlled up for ease of delivery. Upon arrival at the site the panel isexpanded and may be anchored. The panel may be pinned out on theinstallation surface to retain the open cell shape and size beforefilling. Once the panel has been fixed and anchored in place, filling iscarried out e.g. using a bulldozer to deposit soil, sand or other fillermaterial as desired.

There is shown in FIG. 2 a cellular structure in accordance with anembodiment of the present invention. The cellular unit 4 is made up ofinterconnected tubular cells 5, 6 formed of a geotextile material. Thetubular cells 5, 6 have a diameter of 250 mm and a depth of 750 mm. Thecellular unit 4 is taller than the cellular panels typically used incivil engineering applications.

With reference to FIGS. 3a and 3b , the cellular structures of FIG. 2may be formed by taking a strip 3 of nonwoven material and folding itback and forth onto itself. The strip 3 has a depth d of 750 mm. Beforeeach fold, adhesive 7 is applied at a number of spaced apart locationsalong the strip 3. The resultant pleated stack is then openable into apanel 9 having 21 generally tubular, interconnected cells 5, 6 formed bythe folded layers between the adhesive locations. The overall width w ofthe panel 9 is about 1 meter. Adhesive joints formed in this way havebeen found to be up to 85% as strong as the nonwoven material itself. Aspecial adhesive is preferred which can retain its bonding strengthacross a wide temperature range.

According to another preferred method of manufacture the tubular cells5, 6 may be formed individually and then interconnected by stitchinginstead of using adhesive. The choice of sewn joints instead of adhesivejoints may depend on the material used for the cells.

Turning back to FIG. 2, it can be seen that all of the tubular cells 5,6 of the cellular unit 4 are filled with a resilient composite material8 which in this embodiment is a mixture of sand and natural latex. Themixture ratio is approximately 8% of adhesive by weight. Calciumchloride granules or any other suitable catalyst is added to the mixtureat the point of filling to initiate chemical cross-linking of the latexrubber. The resultant composite fill material 8 is solid but porous toliquids and gases. The latex bonding agent acts to bind together thesand particles and to bond the composite 8 to the geotextile fabric ofthe cells 5, 6. Both the composite material 8 and the fabric material ofthe cells 6 are flexible, resulting in an elastic and deformablecellular unit 4.

Of course, the composite fill material 8 may not completely fill eachcell 5, 6. Preferably the composite fill material 8 forms a base and/orupper fill layer for the cells 5, 6. The rest of the fill may be formedby another fill material, such as an unbonded fill material. Onematerial suitable for filling the ‘core’ of the cells is a mixture ofparticulate material such as sand with a binder such as polypropylenefibres.

It will be seen that the cellular unit 4 has an undulating outer surfaceformed by the partly cylindrical tubular cells 5 around the outside ofthe unit 4. The interior of the unit 4 includes generally polygonaltubular cells 6 formed by the intersecting internal fabric walls andbonding points. Whereas the fabric walls of the inner cells 6 areconstrained, the outwardly-facing walls of the perimeter cells 5 aremore free to bulge upon filling, resulting in a curved outer surface toeach perimeter cell 5.

The cells 5, 6 are open at the top and bottom of the cellular unit 4.Thus when the unit 4 is laid on a surface the composite fill material 8is in direct contact with the surface and its conformability provides ahigh coefficient of friction. Alternatively, the cellular unit 4 caninclude a base sheet (not shown) to improve stability for the exposedcomposite 8 on the base of the structure. Such a base sheet ispreferably flexible so as not to reduce the coefficient of surfacefriction. The cellular unit 4 may be placed on such a base sheet priorto filling in order to assist with the manufacturing process. A sheet oflightweight PVC-coated polyester mesh may be used. Other base and/or topsheets can be applied as desired e.g. for particular applications.

The cellular unit 4 shown in FIG. 2 can be deployed on its own e.g. as adefensive unit or it can be stacked with other units to form a largerbarrier structure. The undulating outer surface of the cellular unit 4can provide a cushioning effect. It can also help to interlock adjacentunits in a partially tesselated arrangement.

FIG. 4 shows a cellular structure 10 being stacked on top of anothercellular structure 12. Both structures 10, 12 include interconnectedtubular cells 14, 15 of a flexible geotextile material. The basestructure 12 may be a single cellular unit or it may be made up of morethan one cellular unit stacked side-by-side. The outer cells 14 andinner cells 15 of the base structure 12 are filled with a composite fillmaterial 8 in the same way as is described above with respect to FIG. 2.As before, the cellular structure 12 has an undulating outer surfaceformed by the partly cylindrical perimeter cells 14 around the outsideof the structure 12. The structure 12 therefore provides a cushioningouter surface particularly suitable for use as a crash barrier or thelike. The undulating outer surface can advantageously enhance theresilient response of the structure 12 and could even result indeflection of an impacting body.

The cellular structures 10, 12 shown in FIG. 4 differ from that of FIGS.2 and 3 b in that each structure 10, 12 is provided with a skirting band16 around the upper perimeter of the structure 10, 12. The skirtingstrip 16 can be formed from a different material to the cells 14, 15such as a stiff plastic, e.g. HDPE or PVC, for reinforcement purposes.Due to the solid nature of the bonded composite fill material 8, theskirting strip 16 is not required to prevent particulate materialescaping from between the structures 10, 12, and is preferably omitted.The skirting strip 16 is merely shown for illustrative purposes. Whereemployed, preferably the skirting band 16 is formed from a strip of thesame geotextile material as the cells 14, 15. The skirt portion ispreferably flexible and/or liquid permeable, like the fabric material ofthe cells 14, 15, making it easier to bend the strip 16 around the cellsand tuck the band 16 inside or against the cell walls of juxtaposedstructures. Although the material is flexible enough to allow the band16 to bend into the desired shape, it is also sufficiently stiff thatthe band 16 will hold its shape and lie flat against the cell walls.

The skirting strip 16 is wrapped around the outside of the perimetercells 14 in the cellular structures 10, 12 and fixedly attached to anupper part of the cell walls. The skirting strip 16 may be attached tothe outside of the cells 14 by sewing and/or gluing, for example. Theattachment method used may depend on the respective material(s). Aslotted band 16 may instead be fitted inside the cells 14, adjacent tothe perimeter walls, and fixedly attached if required. Of course, theskirting strip 16 may not extend around the whole perimeter of thestructures 10, 12, and more than one strip 16 may be used.

The skirting strip 16 is attached at the upper end of the base structure12, partially overlapping with a top portion of the perimeter cell wallsand extending above the top of the cells 14 so as to form an upstandingskirt portion. For cells that are 150 cm deep the skirting band 16 maybe, for example, 15 to 45 cm deep, with some of the skirting strip 16overlapping with the cell walls and at least half of its depth leftprotruding beyond the top of the cell walls. The material of theskirting strip 16 is sufficiently rigid that the strip 16 stands upvertically without substantially crumpling or bending.

FIG. 4 illustrates that when stacking two cellular structures 10, 12,the lower portion of the cell walls in the upper structure 10 fit insidethe skirting strip 16 which extends around the perimeter of the lowerstructure 12. The skirting strip 16 may optionally be fixedly attachedto or held against the cell walls of the upper structure 10 by anysuitable means e.g. adhesive, sewing, fasteners, etc. The skirting band16 can help to guide and align the cells when stacking such structures10, 12 on top of one another. The resultant wall or barrier structurewill have substantially vertical perimeter walls on all sides with areinforcing seal being formed by the skirting strip 16 between thevertically juxtaposed structures 10, 12. The skirting portion mayimprove the overall strength and impact resistance of the stackedstructure. However, such a skirting strip or other such seal means is inno way essential, and is in fact omitted in preferred embodiments of theinvention.

As the external skirting strip 16 extends upwardly, the cellularstructures 10, 12 can be stacked or deployed in any order and can beused the same way up in all of the layers, making it simple to constructa stacked system. When a number of structures have been stacked on topof one another, e.g. to form a wall or barrier, the skirting strip 16protruding from the uppermost structure can be folded down to at leastpartially cover the exposed fill material. Folding of the skirt portionis possible due to the flexibility of the fabric material.

Alternatively (but not shown), the skirting band 16 may be integrallyformed with the cell walls e.g. where the structures 10, 12 are formedof a single cellular unit. For example, the perimeter cells 14 of acellular unit may be provided with split wall dimensions. Theinwardly-facing half of a perimeter cell 14 may be of a standard depthmatching the inner cells 14 in the unit while the outwardly-facing halfof each perimeter cell 14 may have an extended wall which is deeper thanstandard, the extended wall portion acting as a skirt.

The upper cellular structure 10 may be stacked on top of the lowerstructure 12 before being filled, as shown, or one or more pre-filledstructures may be stacked up. However, for ease of handling it may bepreferred to manufacture a barrier by filling each cellular structure asit is stacked. Curing of the fill material during stacking canadvantageously provide bonding between the stacked layers.

With reference to FIGS. 5 to 7 a cellular structure 18 in accordancewith a preferred embodiment includes a cellular unit 20 embedded withina load-bearing frame 22. The cellular unit 20 is substantially the sameas that described above with respect to FIG. 2, i.e. the fill material24 is a sand/adhesive composite, and those features described above willnot be repeated. However, the cellular unit 20 may be filled insteadwith a different material, for example a solid particulate material suchas concrete, aggregate, ballast materials (e.g. brick, broken concrete,granite, limestone, sandstone, shingle, slag and stone), crushed rock,gravel, sand, clay, peat or soil, or any mixture of these. As ispreferred, the cellular unit 20 is not provided with any kind ofskirting strip around its upper periphery.

The load-bearing frame 22 includes an outer frame ring 26 to which thereare attached two diagonal cross-pieces 28 which form the base of theframe 22. Four upright members 30 are attached at a lower portion to thecorners of the frame ring 26 and are designed to extend slightly higherthan the cellular unit 20, to allow for coupling to another framestacked above. Further frame rings can be provided, e.g. spaced over thevertical extent of the structure. The frame 22 is sized to generallymatch the perimeter of the cellular unit 20 and to maximise the pointsof the contact between the cellular unit 20 and the frame 22.

The base of the cellular unit 20 is covered by a sheet 21 of flexiblefabric material such as a lightweight PVC-coated polyester mesh. Thebase sheet 21 is too thin to be discernible in FIG. 6. The base sheet 21is inserted inside the frame 22, over the cross-pieces 28, but in analternative embodiment it could extend at least partially beneath theframe ring 26 instead or as well.

It will be understood that the use of two diagonal cross-pieces 28 canstabilise the frame ring 26 to an extent but will still allow the frame22 to twist and bend. In particular, the base of the frame 22 canconform to an uneven surface. The cross-pieces 28 are preferably thinand narrow so as to interfere as little as possible with the contactbetween the cellular unit 20 and the ground, while still bearing theload of the cellular unit 20 and transmitting the load to the rest ofthe frame 22. The frame 22 is preferably made of stiff metal components.

The upright corner members 30 are provided with sockets 32 spacedslightly from the bottom of the frame. The top of each upright member 30terminates in a right angle and a horizontal connector 33 with a hole 34which is arranged align with the socket 32 on a frame stacked above, aswill be explained in more detail below. The upright members 30 are alsoprovided with holes 36 which allow for connection of a top lifting frame37 or other hoisting means, e.g. as shown in FIG. 7. The exemplarylifting frame 37 includes a loop 39 centred over the cellular unit 20which facilitates rapid deployment of the structure 18, for example by afork lift truck, crane or HIAB-equipped lorry. The lifting frame 37 isdesigned to spread the load carried by the supporting frame 22.

The cellular structure 18 is manufactured as follows. The frame 22 isconstructed and a base sheet 21 is inserted inside the frame ring 26, ontop of the cross-pieces 28. Next the cellular sub-assembly of thecellular unit 20 is opened out and stood on top of the base sheet 21,inside the frame 22. The cellular sub-assembly may be provided collapsedin flat-pack form or even flattened and rolled up. To aid in opening outthe cellular sub-assembly, the cells may be pinned open prior tofilling. The fill material 24, for example a mixture of sand and latexadhesive together with a cross-linking catalyst, is then poured into thetubular cells to fill them to the desired level and left to solidify. Ifa particulate fill material is used without a bonding agent thencompaction may be required.

In order to increase the mass of the cellular structure 18 and thecoupling between the cellular unit 20 and the frame 22, the fillmaterial 24 is also preferably poured into the gaps between theperimeter walls of the cellular unit 20 and the frame ring 26. It willbe seen from FIGS. 5 to 7 that the lower end of the cells areeffectively encased by the fill material 24 within the frame ring 26.The fill material 24 may not bond completely to the frame 22 but it willhelp to transmit forces and enable the overall structure to bend andflex in a unified response e.g. to impact.

The cellular structure 18 can be used on its own or in combination withother such structures. The load-bearing frame 22 allows each cellularunit 20 to be more easily handled, e.g. picked up and transported to adesired location for use. As the structure 18 is pre-filled it can berapidly deployed to instantly form a barrier or defensive wall. The sizeof the structure 18 can be adapted depending on its intended use.

FIG. 8 shows one example of how a barrier structure can be built up froma plurality of pre-filled cellular structures 18. In this example, 12cellular structures 18, 18′, each with their own frames, areinterconnected to form a crash barrier capable of passing the BritishStandard PAS 68 vehicle crash test. The structures 18, 18′ may not allhave the same fill material. Each structure 18, 18′ may also contain amixture of fill materials within its cells.

Structures 18, 18′ stacked side-by-side are connected to one another bylink plates 38 which couple adjacent sockets 32. The link plates 38 maybe bolted or screwed against the sockets 32. It can be seen that thebevelled corners of the frame rings 26 leave room for the sockets 32 toabut and space to insert a link plate 38 between them. Link plates 38can be attached both above and below each pair of coupled sockets 32.

An upper structure 18′ can be stacked on top of a lower structure 18with the horizontal connectors 33 and holes 34 at the top of anupstanding member 30 of the lower structure 18 aligned underneath thesockets 32 of the upper structure 18′. The vertically stacked uprightmembers 30 can then be bolted together via the sockets 32 and connectors33. Link plates 38 are used to sandwich the sockets 32 and connectors33. While the connections hold adjacent structures 18, 18′ firmlytogether both horizontally and vertically, the spacing betweenconnections at the corners of each frame 22 ensures that the overallbarrier is not rigid and can still flex upon impact.

It is also shown in FIG. 8 how horizontal struts 40 can be fixed acrossthe top perimeter of a frame 22, extending between the connectors 33,e.g. by bolts 42 passing through the strut 40 and a corner connector 33below. Link plates 38 can be used to span adjacent struts 40 and tocouple together adjacent uprights 30 at the same time. Adjacent frames22 are therefore connected together at both their upper and lower ends,even in the top layer of a stack.

It will be appreciated that FIG. 8 merely illustrates one example of abarrier system and that the cellular structures 18 can be stacked bothhorizontally and/or vertically in as many layers as is desired to form abarrier of desired dimensions.

The invention claimed is:
 1. A structure, comprising: a cellular unitembedded within a load-bearing frame; the cellular unit having (i) anundulating outer surface defined by perimeter cells having outwardlyfacing walls; (ii) a plurality of constrained interior cells surroundedby the perimeter cells, the constrained interior cells interconnected byintersecting internal walls comprising a fabric material; and (iii) acomposite fill material at least partially filling the perimeter cellsand the plurality of interior cells, wherein the outwardly facing wallsare not constrained and are free to bulge with the composite fillmaterial and the composite fill material comprises a particulatematerial; and the load-bearing frame configured to bear a load of thecellular unit and the composite fill material, the load-bearing framecomprising (i) an outer frame ring; (ii) at least one cross-pieceattached to the outer frame ring and configured to pass underneath thecellular unit; and (iii) at least one upright member attached to theouter frame ring and extending in a vertical direction from the outerframe ring; wherein the at least one upright member includes a first endproximate to the outer frame ring and a second end distal from the outerframe member, and wherein the first end includes a socket and the secondend includes a hole aligned with the socket.
 2. A structure as claimedin claim 1, wherein the bonding agent bonds together the particulatematerial, and the bonding agent bonds the composite fill material to thecontinuous fabric material.
 3. A structure as claimed in claim 1,wherein the bonding agent comprises any one of more of an elastomericmaterial, a rubber-based adhesive, a resin comprising flexibleparticles, and a curable material.
 4. A structure as claimed in claim 1,wherein the particulate material comprises sand, the bonding agentcomprises adhesive, and the composite fill material comprisesapproximately 8% by weight of the adhesive.
 5. A structure as claimed inclaim 1, wherein: the composite fill material comprises a materialselected form the group consisting of a reinforcing material and abinding material; or the plurality of constrained interior cells is alsoat least partially filled with a second fill material, the second fillmaterial comprising a material selected from the group consisting of areinforcing material and a binding material.
 6. A structure as claimedin claim 5, wherein the reinforcing material comprises fibres, and/orthe binding material comprises fibres.
 7. A structure as claimed inclaim 6, wherein the fibres comprise synthetic fibres.
 8. A structure asclaimed in claim 1, wherein the load-bearing frame is flexible.
 9. Astructure as claimed in claim 1, wherein the load-bearing frame isresiliently coupled to the cellular unit.
 10. A structure as claimed inclaim 1, further comprising a second fill material disposed in at leastsome spaces between the cellular unit and the frame, wherein the secondfill material is the same as or different from the first fill material.11. A structure as claimed in claim 1, wherein the continuous fabricmaterial is permeable.
 12. A structure as claimed in claim 1, whereinthe fill material is permeable.
 13. A structure as claimed in claim 1,wherein the continuous fabric material comprises a nonwoven material ora geotextile material.
 14. A structure as claimed in claim 1, whereinthe perimeter cells comprise partly cylindrical cells.
 15. A structureas claimed in claim 1, wherein at least one cross-piece comprises atleast one diagonal cross-piece attached between a first corner and asecond corner of the outer frame ring.
 16. A structure as claimed inclaim 1, wherein the at least one upright member extends past thecellular unit in the vertical direction.
 17. A structure as claimed inclaim 15, wherein the at least one diagonal cross-piece comprises two ormore diagonal cross-pieces.
 18. A structure as claimed in claim 1,wherein the fabric material comprises a continuous fabric materialfolded back and forth on itself and bonded to define the intersectinginternal walls.
 19. A structure as claimed in claim 1, wherein thecomposite fill material comprises a particulate material and a bondingagent.
 20. A structure, comprising: a cellular unit embedded within aload-bearing frame; the cellular unit having (i) an undulating outersurface defined by perimeter cells having outwardly facing walls; (ii) aplurality of constrained interior cells surrounded by the perimetercells, the constrained interior cells interconnected by intersectinginternal walls comprising a continuous fabric material folded back andforth on itself and bonded; and (iii) a composite fill material at leastpartially filling the perimeter cells and the plurality of interiorcells, wherein the outwardly facing walls are not constrained and arefree to bulge with the composite fill material and the composite fillmaterial comprises a particulate material and a bonding agent; and theload-bearing frame configured to bear a load of the cellular unit andthe composite fill material, the load-bearing frame comprising (i) anouter frame ring; (ii) at least one diagonal cross-piece attachedbetween a first corner and a second corner of the outer frame ring andconfigured to pass underneath the cellular unit; and (iii) at least oneupright member attached to the outer frame ring and extending in avertical direction from the outer frame ring; wherein the at least oneupright member includes a first end proximate to the outer frame ringand a second end distal from the outer frame member, and wherein thefirst end includes a socket and the second end includes a hole alignedwith the socket.